We paid a little visit to SRAM’s World HQ in Chicago to get a close up look at the new XX1 11-speed mountain bike group, and here are the pics. Plus, we have some updated info on how the cassette mounts, and how they crammed an extra cog on there without making an ultra-narrow chain.
UPDATED: Pic of the Driver Body added at bottom.
The new single-ring XX1 crankset is a simple thing of beauty. Sure, only having to deal with one ring opens a few doors to play with the way the ring mounts, but hopefully the design foreshadows future XX groups. The spider curves and angles, looking very similar to Red, but it’s the backside that’s the real looker…
Bolts thread directly into the chainring, just like XX. The spider is shaped to push the chainring in the right rotation as you pedal, taking a bit of the stress off the bolts. On the forward facing edge, though, it’s open, making ring swaps quick and easy. Just unbolt it, rotate the ring forward and pull it over the spider and crankarm. Reverse the process and you’re rolling again with, pardon the brand speak, just the right gear.
The alternating thin and thick teeth keep the chain in place with minimal lateral movement. It peeled off as easy as ever, but there was only enough side-to-side wiggle to accommodate movement across the cassette’s range. It really does seem like it should negate the need for a chainguide.
The XX1 crankset uses a 76mm BCD in case you’re wondering.
The chain looked pretty much the same as their standard chains if slightly chunkier in appearance. It certainly didn’t seem any more narrow.
Likewise, the XX1 trigger shifter looks more or less the same as the XX one save for graphics. And there’s no front shifter.
Grip Shift will also be offered, but it, along with the rear derailleur weren’t on hand for inspection. All of these are officially prototype “non rideable samples” that supposedly varied a bit from final production, but in ways you won’t notice by looking at them. In other words, we couldn’t weigh them because they may not be representative of the final product. Since the U.S. development team was tied up with the new Red when this project started, the entire XX1 project was run in their German offices. The U.S. group still handles graphics for it, but at the moment, what you see here is the sum total of XX1 parts they have in the U.S.
The XX1 cassette takes their one-piece machining to new levels. Other than the back plate, all cogs are machined from a single piece of steel.
Even the smallest 10T cog is part of the whole!
In order to get 11 normally spaced cogs to fit on a hub, SRAM got creative in several ways. First, they redesigned the freehub body. Called the Driver Body (sadly, they didn’t have an example of this on hand either), it’s a stepped design that gets smaller under the smaller cogs.
The inner “tube” part of the cassette is now the lock ring. Or, more accurately, the cassette itself is the lock ring. The grooves on the very back section slide onto the Driver Body much the same way a typical cassette slides onto a freehub body, except there’s no single small groove that forces the cassette into one place. The threads directly behind those grooves are what thread the cassette onto the Driver Body. The front of the cassette is grooved to accept a standard lockring tool, which is how you tighten it onto the hub.
By eliminating the lock ring, they gained about 1.5mm on the outside edge. According to our tech rundown with DT Swiss, their 11-speed hubs allowed an extra 1.8mm of freehub width. That puts the total at about 3.3mm, not quite enough to add another cog, so…
…SRAM dished the 42T cog (which serves as the backplate) to follow the contour of the spoke angle a bit and take advantage of otherwise wasted space. Brilliant.
Each cassette takes 90 minutes or so to machine. Here’s what the original Red cassette looks like through the stages:
The new Red and the XX/XX1 cassettes get additional machining between the cogs to help clear debris and save more weight.
Until you see it in person, it’s hard to visualize just how big a 42T cassette is. It’s big.
SRAM’s MTB drivetrain product manager snapped this photo for us. It’s the Driver Body’s main assembly, but there’s a smaller part that extends beyond the bearing that’s visible here. This is from a DT hub, not a SRAM one, and possibly pre-production since it does have the one smaller flange at the back end.